1. Field of the Invention
The field of the invention is data processing, or, more specifically, methods, apparatus, and products for identifying a signal on a printed circuit board (‘PCB’) under test.
2. Description of Related Art
A tester approaches a PCB with a test probe. The PCB has hundreds of vias accessible to the probe at test points on the PCB, the vias connecting through the laminate layers of the PCB to ball contacts in ball grid arrays (‘BGAs’) on one or more flip chips mounted somewhere on the PCB. The tester contacts a test point with the probe and turns to look at a test monitor, an oscilloscope display on which is now displayed the test signal from the test point on the PCB. Here's the problem: What signal is it? What signal does the tester expect to see on the monitor? To which pin on which integrated circuit package is the probe now connected? To which of the hundreds of conductors in fifteen layers of laminate in the PCB is the probe now connected? In high speed electrical lab validation, pins in a BGA or connectors are notoriously hard to identify and probe in a lab environment. The boards, the chip carriers, or the chips themselves, all described in detail in a Computer Aided Design (‘CAD’) file may be installed in the system in a different orientation than is shown in CAD file. The boards, the chip carriers, or the chips themselves may be flipped over or rotated, for better access. A chip package can have several hundred pins, spaced at a very narrow pitch, making it hard to keep track of the intended pin to be probed. A PCB that would otherwise have silkscreened signal identifiers silkscreened onto a surface of the PCB may have no space around a particular chip to insert silkscreen text, or silkscreened text may be covered by an overhanging heat sink or other component.